Philippe Coulon, Presenter: Employee, Koninklijke Philips Electronics NV

Alain Vlassenbroek PhD, Abstract Co-Author: Employee, Koninklijke Philips Electronics NV

Galit Kafri PhD, Abstract Co-Author: Nothing to Disclose

Amiaz Altman PhD, Abstract Co-Author: Employee, Koninklijke Philips Electronics NV, Haifa, Israel

Jacob Sosna MD, Abstract Co-Author: Research grant, Koninklijke Philips Electronics NV Consultant, Carestream Health, Inc Consultant, ActiViews Ltd

Laurent G. Lemaitre MD, Abstract Co-Author: Nothing to Disclose

Yoav Bar, Abstract Co-Author: Consultant, Koninklijke Philips Electronics NV

et al, Abstract Co-Author: Nothing to Disclose

The knowledge of the composition of renal stones is an essential part in treatment and prevention. Renal stones composed of different materials can show similar densities on conventional CT but different attenuation ratio between low and high energy x-rays. The purpose of this study was to build a stone library based on phantom measurements that could be used to automatically predict patients' stones composition with a dual-energy MDCT.

Feasibility study was performed using a single source dual-layered dual-energy MDCT prototype (Philips Healthcare). 36 stones of pure composition known from Infra Red Transmission Spectroscopy (IRTS) analysis were scanned in water and Plexiglas phantoms of 15, 24, 28 and 32 cm diameter. Study parameters were 1mm slice thickness, 0.5mm increment, 140kVp, and 200mAs. The attenuation ratio between low and high energy images characteristic of each stone composition was measured using the Spectral Extended Brilliance Workspace prototype workstation.

The average attenuation ratio increases between 0.5, 0.8 and 6.2% when the phantom size decreases from 32 cm to 28, 24 and 15 cm respectively. For phantom size between 24 and 32 cm, representative of usual patient abdomen attenuation, the stones could be separated into 3 groups of significantly different attenuation ratio: <1.1 Uric Acid (Av 0.99, SD 0.016, 6 stones), 1.15-1.25 for Cystine (Av 1.21, SD 0.022, 6 stones), >1.25 for calcified stones including Brushite (Av 1.30, SD 0.000, 3 stones), Weddellite (Av 1.31, SD 0.013, 5 stones), Whewellite (Av 1.32, SD 0.021, 6 stones), and Carbapatite (Av 1.35, SD 0.023, 5 stones). Only Struvite stones (Av 1.31, SD 0.064, 5 stones) had attenuation ratio overlap with Cystine and calcified stones but can be identified from infection history.

Our preliminary results suggest that renal stone composition can be characterized with dual-energy MDCT. Large scale studies including patients scanned before stone ablation and analysis by IRTS are underway to check the sensitivity and specificity of the method.

Dual-energy MDCT may be used as a clinical tool for analysis of kidney stone composition, adding information to findings from conventional CT performed for nephrolithiasis.

Coulon, P, Vlassenbroek, A, Kafri, G, Altman, A, Sosna, J, Lemaitre, L, Bar, Y, et al, , Prediction of Renal Stone Composition Using Dual-Energy MDCT and an in Vitro Reference Library.  Radiological Society of North America 2008 Scientific Assembly and Annual Meeting, February 18 - February 20, 2008 ,Chicago IL. http://archive.rsna.org/2008/6016622.html